This renewal proposal is to continue with three activities related to the diagnosis and differential diagnosis of neoplasic disease of bone. (1) The continued collection of data base and experience in the diagnosis and differential diagnosis of neoplastic disease of bone, through the activities of the Mid America Bone Diagnostic Center and Registry. During the past 3 years, this activity has led to the establishment of a high quality, rapid referral service for suspected neoplastic lesions of bone. This activity is highly valued for its documentation, continued testing of computer diagnostic technology, and of basic diagnostic concepts. (2) The development of a global computer diagnostic concept, based on the L-Bayes principle, which permits the diagnosis and differential diagnosis of all skeletal and parosteal lesions of bone, and which provides for addition, on future occasion, of disease entities in the metabolic and arthritic domains. (3) A comprehensive study of the dyplastic lesions of bone through the development of a data base from the Langer collection, and the development of an appropriate logic for separating these entities into meaningful catagories. Mathematical studies of the slope of the metaphyseal curve of the distal femur, work undertaken to provide better differential diagnosis of the dysplasias, has yielded an exciting new approachs which is to be further pursued.